This project deals with the interactions of tobacco mosaic virus and its components: virus-virus interactions, protein-protein interactions, RNA-RNA interactions, protein-RNA interactions and the interactions of the virus and its components with ions, especially divalent cations and hydrogen ions, with organic molecules and with other proteins. Of special concern is the energetics of TMV protein polymerization. Plans for the coming year include study of hydrogen ion binding during polymerization of TMV protein and comparative study of the polymerization of coat proteins from strains of TMV, especially those with known differences in amino acid composition leading to a net charge different from that of type strain coat protein. Other plans include specific ion binding studies by virus, protein and RNA and also an investigation of conformational changes associated with virus protein polymerization. BIBLIOGRAPHIC REFERENCES: John C. McMichael and Max A. Lauffer, "A Specific Effect of Calcium Ion on the Polymerization-Depolymerization of Tobacco Mosaic Virus Protein", Arch. Biochem. & Biophys. 169, 209-216 (1975). Max A. Lauffer, "Entropy-Driven Processes in Biology: Polymerization of Tobacco Mosaic Virus Protein and Similar Reactions", No. 20 of Springer series on Molecular Biology, Biochemistry and Biophysics (1975).